Preparation And Property Study Of Polymethylsilsesquioxane And Their Composites

Silica aerogels,which are non-crystalline solids with a three-dimensional network of interconnected nanometer-sized primary particles,have high porosity?⁹9.8%?,specific surface areas?55-1250 m²/g?,low density?⁰.003-0.500 g/cm³?,thermal conductivity?0.005-0.100 w/?mk??,low dielectric constant?1.0-2.0?and high transmittance?⁹3%?.Due to their such unusual characteristics,much attention has been given to silica aerogels in recent years for their use in several technological applications including high energy physics,catalysis,energy storage,space exploration mission,gas filtering,drug delivery and adsorption,and so on.However,the skeleton of the SiO₂ aerogels was formed by the secondary particles,which connection between the particles and the particles was linked by chemical bond or hydroxyl bridge.The chemical bond was constituted by hydroxyl and Vander Ed Ley.The unique structure of accumulation,which was a source of its low strength and high brittleness.Moreover,after hydrolysis and condensation,the-OH on the surface of the aerogel leads to the hydrophilic properties of the aerogel.In a word,the inherent brittleness and hygroscopicity of silica aerogels lead to difficult processing,pressure crushing and poor environmental stability.In this paper,we report novel flexible and hydrophobic monolithic aerogels derived from a simple one-step sol-gel route starting from a single trifunctional precursor-methyltrimethoxysilane?MTMS?.Moreover,we solved the problem of the phase separation of the silica wet gel derived from the three-functional silicon source.We reported a novel method for the amine-modification of a native silica aerogel at 0?compared with the traditional method at the harsh temperature of-77?.In this case,the tetraethylorthosilicate?TEOS?and methyltrimethoxysilane?MTMS?were both used as the co-precursors instead of the traditional tetramethoxysilane?TMOS?,which was attributed that the hydrolysis and condensation of TEOS was slower than that of TMOS and each MTMS monomer had one non-hydrolyzable methyl group.After the isocyanate cross-linking,the modified silica aerogel could achieve the of hydrophobicity of 155.7°and specific modulus?modulus/density?of 444.93.Furthermore,properties of being a super hydrophobic,mechanically strong multifunctional silica-based aerogel were enhanced.